A mortar training device utilizes a fuzed subprojectile containing a percussion cap and spotting charge. The subprojectile and a propelling charge are assembled within a full size dummy projectile having a subcaliber bore. The training device resembles a service mortar cartridge and is dropped fired into a mortar in the same manner as with service ammunition. The dropped training device strikes a firing pin at the base of the mortar to initiate a propelling charge. The charge propels the subprojectile into a trajectory downrange while ejecting the dummy projectile a few yards from the mortar. The subprojectile impacts the ground to initiate the percussion cap which in turn ignites the spotting charge. The distance of impact is approximately one-tenth the distance of service ammunition. The training device is intended to provide realistic mortar firing training, at low cost, using standard mortar, standard sighting and fire control equipment and a special firing table in the same manner as standard service mortar ammunition.
A current design for initiating the spotting charge in the subprojectile includes an internally housed plunger in which the percussion cap is mounted. Upon projectile impact, the plunger slides forward causing the percussion cap to strike a firing pin.
The plunger is firmly held in a rearward seated position during handling and launch by radially emplaced balls within throughholes in walls of the subprojectile with the balls partially extending into a recess in the plunger. The balls are held in place by an overlying cartridge during handling and by the bore during launch. The balls discard from the subprojectile upon clearing the bore.
The design relies on impact deceleration of the subprojectile together with an inertial mass of the percussion cap plunger to provide the necessary striking impulse for initiating the percussion cap. A disadvantage of the design is that the striking impulse thusly generated is low, and occurence of dud projectiles are often encountered during practice firing exercises.
The above design appears to provide a requisite safety in handling and reliability in arming, but there is a need to reduce incidence of duds.